During the transfer of a volatile liquid such as gasoline or a similar fuel from a storage facility, there is normally an unsealed connection made between the disconnectable nozzle and the tank being filled. As the transfer operation progresses, residual gases contained in the tank, as well as air, normally rise into the atmosphere.
Many municipalities and governmental agencies have proposed or adopted regulations intended to reduce or at least control these emissions. One method toward complying with mandated regulations is the provision of a completely closed system between the fuel source or storage facility and the tank being filled.
Such a closed system normally includes a conduit which carries fuel, having a manually operated dispensing nozzle attached to the conduit remote end. The latter is adapted to be removably positioned in the filler pipe of the receiving tank. It further includes means to form a sealed engagement between the nozzle spout and the tank filler tube.
Also in many instances, a system of the type contemplated is not entirely closed in a true sense, but rather is vented to the atmosphere. With such an arrangement, as liquid is pumped from the storage facility, either of two eventualities could occur. If fuel leaving the system is not immediately replaced by vapor from the tank being filled, air will be drawn into the system. On the other hand, when excessive vapors are drawn from the tank being filled, some will have to be vented. However, these exiting fumes will first be treated such that their discharge is not harmful to the environment.
Several embodiments of nozzle sealing arrangements have been found to be advantageous for providing the necessary vapor tight, yet disconnectable connection at the nozzle spout. One method for providing the desired seal is to attach a cylindrical, flexible walled member such as a rubber boot or the like, to the fuel dispensing nozzle. The boot in such a position will substantially surround the nozzle spout when the latter is in place.
By use of such an arrangement, when the nozzle is received in the filler pipe of the receiving tank, the walls of the flexible boot will be deflected and/or distorted. The boot will thereby define an annular vapor passage while the resilient contact edge thereof sealably engages the tank filler pipe.
This type of arrangement has generally been found to be highly effective. Thus, when a fuel flow is introduced from the nozzle into the receiving tank, normally a slight pressure is produced within the tank. This pressure will displace fuel vapors as well as air.
The displaced vapors will be urged upwardly through the annulus defined by the nozzle spout and the flexible member. Said vapors can then be transferred by way of the dispensing nozzle through a separate conduit, to the fuel source, or to another reservoir for retaining the vapors.
The effectiveness of this system depends to a large degree on the mechanical compatibility of the vehicle with the nozzle, i.e., to permit a tight seal at their interface. If for any reason the contact edge of the nozzle boot cannot firmly engage the filler pipe, a seal cannot be achieved, and a leak will result or develop.
The presently disclosed arrangement is designed to reduce the unfavorable effect of such leaks by applying a slight vacuum within the nozzle boot. The vacuum assists the vapor transfer toward the intended storage means. In the presently disclosed arrangement, a system is provided which incorporates a number of features including: (1) a removable seal at the vehicle-nozzle interface for those vehicles which permit such a seal; (2) a vacuum assist device adapted to aid in collecting vapors from those vehicles which cannot be completely sealed, and (3) the use of a vapor pump, which is driven in response to the flow of dispensed fuel, to carry off fumes.
Said pump is driven by a hydraulic motor within the system, thereby to substantially regulate the volume of vapor which is moved, in relation to the volume of fuel dispensed. The system further contemplates a valved bypass conduit which opens in response to an accumulation of liquid in the vapor system, and which returns said liquid to the main tank or reservoir.
Toward assuring the operation of the overall system under varying circumstances, the valved bypass conduit is provided across the positive displacement vapor pump to pass vapors directly to the pump outlet side if conditions require, and to keep liquid out of the vapor pump. Toward that same end, the vapor pump outlet is communicated, through an adjustable valve, to the vapor pump inlet so that the desired ratio of gases ingested at the nozzle with respect to the amount of liquid dispensed can be adjusted to some pre-selected ratio at the time of calibration. Further, a one-way mechanism may be installed in the vapor pump inlet line to prevent vapors from escaping when the dispensing system is not being operated.
An object of the invention therefore is to provide a vaporizable fuel system which embodies an effective sealing means disposed between the fuel dispensing nozzle and a receiving tank. A further object is to provide a balanced fuel system of the type contemplated which is enhanced in response to the inflow of fuel to the receiving tank. A still further object is to provide a vacuum assist arrangement within a fuel system having a dispensing nozzle, which assistance is adjusted in response to the flow of gasoline to the tank being filled, and to the volume of vapor which is displaced from the tank during the operation.